spaceprovided) Smoking is a serious problem in the United States both in terms of health risks to the individual and financial cost to society as a whole. Impulsivity, a behavioral risk factor, has been shown to be higher among drug abusers than non-users (including smokers vs. non-smokers or ex-smokers). Given the link between smoking and impulsivity, a thorough investigation of the specific behavioral mechanisms affected by nicotine is needed to better understand the conditions leading to smoking acquistion, maintenance, and relapse. The present proposal includes two experiments aimed at isolating the effects of nicotine on amount and delay sensitivity: the primary behavioral mechanisms involved in impulsive choice. Experiment 1will identify what effect nicotine has on amount and delay sensitivity. Experiment 2 will test a procedure for rapidassessment of delay and amount sensitivity changes which could be easily adopted by other researchers interested in examining the behavioral mechanisms affected by other drugs of abuse. PHS416-